1. Field of the Invention
The present invention relates to an original feeding apparatus having a plurality of sensors for detecting an original.
2. Related Background Art
Some conventional original feeding apparatus to be mounted to a copying machine have a plurality of sensors and a plurality of motors. Recently, as sensors provided on an original tray and in an original convey path, a sensor in which a light emitting element and a light receiving element are arranged so that light emitted from the light emitting element is reflected by an original and then is received by the light receiving element or a sensor in which a light emitting element and a light receiving element are arranged so that light from the light emitting element to the light receiving element is blocked by an original has been used. In sensors of type in which paper such as an original exists between the light emitting element and the light receiving element, since paper powder can easily be accumulated on the light emitting element or the light receiving element, control is effected in such a manner that a light emitting amount of the light emitting element is increased if a light receiving amount of the light receiving element is decreased by influence of the paper powder.
However, while electric power is being supplied to the original feeding apparatus, high electrical current must continue to be flown in order to enhance the light emitting amount of the light emitting element, with the result that a service life of the light emitting element may be shortened. Japanese Patent Application Laid-Open No. 2000-289885 discloses an original feeding apparatus having a sensor including a light emitting element and a light receiving element and teaches the fact that the original feeding apparatus is provided with a logic type power supply including a sensor and a power type power supply including a motor, and the power type power supply is turned OFF when an original is not set on an original tray. But, since it is assumed that the logic type power supply is always turned ON, although effect regarding power consumption is excellent, a problem regarding a service life has not yet been solved.
An object of the present invention is to provide an original feeding apparatus in which the above-mentioned problem is solved.
Another object of the present invention is to provide a sheet feeding apparatus comprising a first detector for detecting presence/absence of a sheet, a second detector capable of being electrically switched between a detection possible condition that the presence/absence of the sheet can be detected and a detection impossible condition that the presence/absence of the sheet cannot be detected, and a controller for changing the second detector to the detection impossible condition even when the first detector is in a detection possible condition.
A further object of the present invention is to provide an original feeding apparatus comprising a first detector for detecting presence/absence of an original, a second detector capable of being electrically switched between a detection possible condition that the presence/absence of the original can be detected and a detection impossible condition that the presence/absence of the original cannot be detected, and a controller for changing the second detector to the detection impossible condition even when the first detector is in a detection possible condition.
The other objects and features of the present invention will be apparent from the following detailed explanation referring to the accompanying drawings.